HEAD requests with PHP-FPM

I would like to be able to support HEAD requests. For the most part, HEAD works well with static files. However, if I am trying to use a HEAD request against a PHP file, it is missing the Content-Length or the Transfer-Encoding header.

PHP-FPM is connected to nginx 1.2.8 using FCGI. I also have gzip enabled.

What's the reason for nginx not including the Transfer-Encoding header? Is there anyway to turn it on? Interestingly, if I try and set the Transfer-Encoding header inside the PHP script, it is still removed by nginx.